Characterization of the L1NH repeat family of Novikoff hepatoma.

Long interspersed repeated sequences of the Novikoff hepatoma rat tumour cell genome were cloned and studied. No basic differences were found when the genomic organization of the Novikoff hepatoma was compared with that of other mammalian L1 families. The nucleotide sequence of the central approximately 4 kb (1 kb = 10(3) bases) part of the Novikoff hepatoma LINE (L1NH) appeared to be more highly conserved than the sequences found at the 5' and 3' ends. Moreover, the central approximately 4 kb core fragments were not always associated with the same end sequences. Thus, the occurrence of the more-conserved and more-abundant central portion in L1NH suggest that: (1) besides reverse transcription, other DNA- and/or RNA-mediated mechanisms might be involved in the dispersal of LINE families; and that (2) L1 sequences can sometimes consist of a compound unit made up of members of different L1 subunits and sequences with different genomic copy numbers.